In many medical applications, a polymer composition constituting at least a part of a medical device, such as a hydrophilic coating, a hydrogel, a scaffold, an adhesive, etc., is intended to be in intimate contact with the human body. Medical devices may be intended for introduction into, covering, or filling human cavities. Examples of cavities, or openings, may be naturally occurring cavities such as urethra, mouth, ear, nose, eye, rectum, or it could be man-made openings made by surgery or as a result of a planned action, e.g. a cavity or an opening in an artery, a vein, a lymph node, or an opening in the gastrointestinal tract, such as a colostomy, ileostomy, urostomy or an opening or cavity resulting from a non-anticipated action. Said medical device or the polymer composition may also be used for location between extremities (legs, fingers, toes, armpit) or for physical attachment to the human body as a result of the involvement of an adhesive.
Polymer compositions of medical devices can be engineered to be soft and flexible, and to reduce friction between sliding parts. For example, it is known to coat medical devices, e.g. catheters for introduction into human cavities such as blood vessels, digestive organs and the urinary system, with a hydrophilic coating. When the coating is swelled with an aqueous solution or water, the surface of the medical device becomes slippery and is well suited for a painless introduction into a cavity with minimum damage on tissue.
Where a device of said type, e.g. a catheter with a hydrophilic coating, is introduced into a human cavity, the normal human defense barrier may be penetrated resulting in introduction of microbes, i.e. small cells such as vira, bacteria, fungi, mold, bacteriophages, or tissue-like or multiple organized cells. It is well known that persons practicing intermittent urethral catheterization as a daily routine often have problems with symptomatic urinary tract infections (UTI). Similarly, a number of other medical devices that come in intimate contact with human tissue can cause microbial infections.
Hydrogen peroxide is known to have an anti-microbial effect. It is also known to decompose easily. By reaction with reduced transition metal ions such as iron (II) and copper (I), hydrogen peroxide decomposes by the Fenton reaction to form the highly reactive hydroxyl radical. Apart from destroying hydrogen peroxide and hence reducing the shelf-life of a product comprising hydrogen peroxide, hydroxyl radicals from the Fenton reaction may potentially damage a polymer coating, in particular a hydrophilic coating, by way of its reaction with various components of the coating system. Contamination of water with transition metal ions takes place, e.g. by storage of the water in steel tanks or in glass. Even in water that is purified, e.g. by ion exchange, trace amounts of transitional metal ions are still present. Thus, a polymer coating comprising a liquid comprising hydrogen peroxide may generally be considered unsuited for long time storage.
U.S. Pat. No. 5,130,124 discloses a stabilized film-forming antimicrobial composition of hydrogen peroxide.
U.S. Pat. No. 5,951,458 discloses a method of inhibiting restenosis by application of an oxidizing agent to blood vessels, e.g. by delivery of hydrogen peroxide via a balloon catheter. The US-patent does not address the problem of stability of hydrogen peroxide when present in a hydrophilic coating.